The present invention relates to speaker cabinets for audio equipment and the like.
As outer walls of speaker cabinets, there have been employed cabinet boards typically made by adhesively bonding a decorative sheet or plate to the surface of a relatively heavy and hard base member, such as a plywood board, single-panel sheet (in this case, veneer sheet) or particle board, in a laminated fashion. The thus made cabinet board is cut into predetermined sizes and shapes to provide a front plate, left and right side plates, back plate and bottom plate, and these plates are jointed together at their edges to thereby provide a speaker cabinet having a rectangular parallelepiped shape. The speaker cabinet has a front covered with a grill net, and various kinds of speakers are accommodated in the interior of the speaker cabinet. Such speaker cabinets are disclosed, for example, in Japanese Patent Application Laid-open Publication Nos. HEI-7-030987, HEI-10-322787, HEI-5-153681 and 2003-116189. Also known are speaker cabinets of other shapes than the rectangular parallelepiped shape, such as cylindrical and near-cylindrical shapes, which are formed by curving the cabinet board to have a convexly curved outer surface (i.e., obverse surface) (see, for example, Japanese Patent Application Laid-open Publication Nots. 2002-252891 and HEI-6-351088 and nonpatent literature “Q series Speaker Cabinet” by KEF Ltd.).
The precent invention particularly concerns one of the types of speaker cabinets which is at least partially formed of a cabinet board arcuately curved to have a convexly curved outer surface (i.e., obverse surface) and which is constructed to have a high mechanical strength and high-quality outer appearance.
FIG. 5 is a sectional view of an example of the conventional curved-type cabinet boards for use as an outer wall of a speaker cabinet. The cabinet board 1 is made by forming a base member 2 with four plywood hoards 2a–2d and adhesively bonding a decorative sheet 3 to the outer surface of the base member 2 in a laminated fashion. The thus-made cabinet board 1 is then pressed and arcuately curved by a press forming machine so that it assumes a convexly curved outer surface of a predetermined radius of curvature.
FIG. 6 is a sectional view of another example of the conventional curved-type cabinet boards. The cabinet board 7 comprises a base member 5 in the form of a veneer sheet, particle board or the like, which has a plurality of grooves 6 formed at predetermined intervals in its reverse side that makes the inner side of the speaker cabinet. The cabinet board also includes a decorative sheet 3 adhesively bonded to the outer surface of the base member 5. The cabinet board 7 is then pressed and arcuately curved by a press forming machine so that it assumes a convexly curved outer surface of a predetermined radius of curvature. The cabinet board 7 of this type is employed, for example, in speaker boxes manufactured by KEF Ltd. Because of the press-curving, each of the grooves 6 is formed into a relatively small opening width.
However, the conventional curved-type cabinet board 1 of FIG. 5, where a plurality of the plywood boards 2a–2d are used as the base member 2, is disadvantageous in that it achieves only low productivity and needs a large-size forming machine, because it not only has to undergo a considerable number of adhesive applying steps but also has to be subjected to great curving pressure for a long time due to its high rigidity.
On the other hand, the conventional curved-type cabinet board 7 of FIG. 6, which comprises a smaller number of components than the cabinet board 1 of FIG. 5 due to the provision of the grooves 6, is advantageous in that, by virtue of lower overall rigidity, it can be readily formed into a curved shape with a smaller pressing force. But, as the cabinet board 7 is press-curved, strese builds up concentratively in outer surface regions 9 of inter-groove portions 5a (i.e., non-grooved portions between the grooves 9) of the base member 5 which correspond to opposed side edges of the grooves 6. Thus, the base member 6 would be undesirably bent at the outer surface regions 9, so that the decorative sheet 3, formed of a polyvinyl chloride (PVC) or other flexible material, would also bend to leave undesired creases 10. Consequently, the cabinet board 7 can not have a high-quality, smooth convexly curved outer surface, which would result in a low-quality outer appearance of the cabinet. However, because a grain pattern is normally printed on the surface of the decorative sheet 3, the creases 10 would not be readily perceived visually and thus would be rarely recognized as significant defects.
Furthermore, the grooves 6, opening in the reverse side of the base member 5, decreases the rigidity of the cabinet board 7, and thus, acoustic characteristics of the speaker cabinet would be deteriorated if the grooves 6 vary in width as the cabinet itself resonates with sound waves radiated from a speaker diaphragm.